Various embodiments of a braking system for a motor vehicle are described herein. In particular, a braking system for a motor vehicle includes a hydraulic circuit for producing a braking force, the hydraulic circuit having a pressure source for producing a hydraulic pressure and a pressure store, the pressure store of the hydraulic circuit being able to be supplied with hydraulic fluid from a delivery side of the pressure source if necessary.
A braking system of this type is already known from the prior art. For instance, document DE 103 18 850 A1, and corresponding U.S. Pat. No. 7,296,861 B2, both of which are incorporated by reference herein, discloses a braking system in which the pressure store can be supplied with hydraulic fluid in accordance with the servo pressure present in the servo pressure circuit. The pressure store serves to compensate for pressure fluctuations in a braking operation. This prior art makes provision for the pressure store to be supplied with hydraulic fluid substantially only when the hydraulic pressure provided by the pressure source is freely available and does not have to be used in another manner, for example, in the context of a braking operation. However, this arrangement has the disadvantage that the pump must be constructed so as to be relatively powerful since the pressure differential present at the pump is relatively large. The pump has to pump hydraulic fluid from the pressure-free fluid reservoir into the servo pressure circuit which is in a state of relatively high pressure. Furthermore, owing to the relatively high pressure differential between the intake side and the delivery side, particularly at the beginning of the braking operation, the pump must be able to react in a very dynamic manner. The pump which must be constructed so as to be correspondingly powerful leads to increased costs for the braking system. Furthermore, when the pump is driven, the on-board electrical power network is also placed under relatively high loads.
A similar arrangement is further disclosed in the document GB 2 132 294A. In this document, the pump which must be constructed so as to be relatively powerful also conveys hydraulic fluid from the pressure-free pressure store into the fluid system which is in a state of relatively high pressure. The same disadvantages arise as set out above for the braking system according to DE 103 18 850 A1.
With regard to additional prior art, reference is generally made to the documents DE 195 42 656 A1, and corresponding U.S. Pat. No. 6,290,307 B1, both of which are incorporated by reference herein, DE 103 37 511 A1 and DE 103 11 060 A1, and corresponding U.S. Pat. No. 7,127,891 B2, both of which are incorporated by reference herein, which all disclose braking systems wherein a pressure store alone can be coupled or is coupled to the delivery side of the pressure source.
Finally, document DE 38 14 045 A1, and corresponding U.S. Pat. No. 4,950,038, both of which are incorporated by reference herein, discloses a braking system having an intermediate fluid store, the hydraulic fluid which is temporarily stored therein in a substantially pressure-free state being permanently available at the intake side of the pump.